GDC 2004: Half-Life 2 Source Engine Demo

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Valve talks about the tech behind the game.

By Tal Blevins

Today at the Game Developers Conference in San Jose, CA, Valve Senior Engineer Rick Ellis gave a presentation highlighting the features of Valve's Source engine, the backbone of such games as Half-Life 2, Troika's upcoming Vampire: The Masquerade - Bloodlines and an as of yet unannounced RPG title from Arkane Studios, the folks behind Arx Fatalis. While the demonstration was aimed at the game development community and it only included video from the E3 demonstration, we did get to see the technology behind the engine in a little more detail.

The demonstration was split into several parts, highlighting the renderer, physics, AI, character expression/emotion, sound and multiplayer features of the Source engine, as well as highlighting some of the built-in world creation tools available to developers.

The renderer portion started with a demo of an outdoor area which showed some of the various graphical aspects of the engine, such as bump-mapping, sub-divided surfaces and light blooming. We also got another glimpse of the materials demo from last year's E3 where Gordon walks through a hallway of various hanging materials such as stone, water, stained glass and a security monitor complete with the ominous-looking G-Man. Rick also showed off that these materials could be used on a variety of different skins, and showed us a model of a human done in all water textures standing in lapping flames. Although we saw this last year, it was still impressive to see again today, and the Source engine is still impressive graphically.

During the physics demo, we learned that game developers can enable and disable the physics on certain items at will, which can significantly increase system performance. We saw the vehicle demo in motion again as well, and learned that such properties as tire friction and material, spring tension, gearing and shift speed were all tweakable in the engine, and how all affect the physics of a given vehicle. Rick also mentioned that you can build four or two-wheeled vehicles in the Source engine (Gordon on a chopper, perhaps?), and that you can have multiple people in a single vehicle. Although he didn't mention Half-Life 2 specifically when talking about multiple players in one vehicle, this does lead us to believe that it may be possible to have both a gunner and driver in the multiplayer portion of Half-Life 2 -- at least we're hoping. We also saw the Manipulator gun in action again, as Rick showed a video of Gordon picking up items with a stream of energy and using them as both a shield against attacks and as a projectile to toss at enemies.

During the AI portion, the focus was on battle and squad AI, and Rick stressed once again for us that the AI in Half-Life 2 is complete dynamic, and that nothing we were seeing was scripted. He also mentioned that, using the Source engine, enemies can detect you based on sight, sound or smell, and showed the Antlion demo where Gordon is using the pheromone grenades to control a group of aliens against emplaced turrets.

The G-Man and Alyx were both featured in the character expression part of the presentation, and we can truly say that Half-Life 2 sports the most realistic character models in any game. Much of the realism is gained through the use of facial expressions as well as the eyes of the characters, which contain the proper bulge of human eyes allowing for realistic reflections from the so-called windows to the soul. The facial expressions in Half-Life 2 are all based on the work of Dr. Paul Eckman's work at the University of California on the taxonomy of facial expressions, and it is amazing just how much emotion the models can express with 40 animated facial muscles, ranging from noticeable sadness to anger to giddiness.

While there were no visual or auditory demos for the sound, multiplayer and toolset portions, Rick did say that the Source engine supports DSP, 5.1 surround sound and that the multiplayer code - the same in use in Counter-Strike, is optimized for even 56k connections. He also touted the Hammer utility, which developers and modders can use to create WYIWYG environments on the fly, as well as a distributed map builder which uses multiple PCs to render a map, reducing the time of map compiling from hours to minutes, so developers can see any changes they make to a particular level much faster than before.

To check out the demonstration for yourself, just click on this link and start with the downloading.